1. Technical Field
The present invention generally pertains to devices and methods for the control of noise, vibration and harshness. More particularly, the present invention is related to a drivetrain component for a vehicle which adaptively controls noise vibration and harshness transmitted to a vehicle passenger compartment. The present invention also pertains to a method for analyzing the effect of a drivetrain component on the level of noise, vibration and harshness transmitted to a vehicle passenger compartment.
2. Discussion
Modernly, vehicle consumers and vehicle manufacturers have become increasingly aware of the desirability for a vehicle passenger compartment that not only feels comfortable and has an aesthetically pleasing appearance, but also is as free as possible from noise which emanates from the exterior of the vehicle passenger compartment. Consequently, vehicle manufacturers expend considerable resources to eliminate or dampen vibrations to prevent the transmission of noise, vibration and harshness (NVH) into the passenger compartment.
Conventionally, dampers or other mechanical vibration absorbing devices have been employed to dampen vibrations to prevent the transmission of NVH into the vehicle passenger compartment. This approach, however, has several drawbacks. One such drawback is that these devices are usually tuned to a specific frequency and consequently, will only dampen vibrations within a relatively narrow frequency band. Accordingly, these devices are typically employed to effectively dampen vibrations at a single critical frequency and offer little or no dampening for vibrations which occur at other frequencies.
Another drawback with conventional mechanical dampening devices relates to their incorporation into an application, such as an automotive vehicle. Generally speaking, these devices tend to have a relatively large mass, rendering their incorporation into a vehicle difficult due to their weight and overall size. Another factor that frequently arises with the incorporation of these devices into a vehicle relates to their positioning in the vehicle. Frequently, it is not possible to mount these devices in the position at which they would be most effective as these same points may be in use for supporting the vehicle body or because the size of the device will not permit it to be packaged into the vehicle at a particular location.
Recognizing the limitations of mechanical dampening devices, another technique has been proposed wherein unwanted noise is canceled out by a sound wave that is equal in amplitude but shifted out-of-phase by 180 degrees. This approach, too, has several drawbacks which significantly limit the overall effectiveness with which this technology may be successfully integrated into a vehicle. Several of the more significant drawbacks stem from the fact that the vibrations which cause NVH in the vehicle passenger compartment are still being generated. Consequently, it is still necessary to employ mechanical damping devices to attenuate the vibration that is transmitted into the vehicle passenger compartment. Another drawback associated with this approach is its broad-based effort to mask all noise regardless of the source of the noise. Consequently, these systems lack a mechanism which enables them to accurately predict the amplitude and frequency of the noise, thereby limiting the effectiveness with which they are able to mask the noise.